RAM upgrade woes - please help

Well, decided to bite the bullet this evening and add another 16Mb of RAM. Seemed to go okay, if a bit fiddly, but no bootup! I was getting a blue light on the main board, and the pulsing blue on the display board, but no serial output.

On checking, it looks like I had shorted pin 123 and 124 on the ARM.

Sadly, in trying to remove the short, I now have no boot up, no blue lights, nothing. Think there is a short across other pins around 123.

My solder wick and other tools are just not small enough to sort this out - so if anyone UK based can help me out I'll provide some reward. I'm fairly certain that is all there is that is wrong.

Need to dig out my backup empeg and bring it up to date until I can get this sorted out (think it is still on 2b3)

While I cannot help with the recovery of the hardware, I would recommend that you just "transplant" the drives from your current empeg to the backup one. And then just flash the appropriate kernel.

Try soaking the wick with flux first. It will come out. Shorting pin 124 to pin 125 would do that.

Ahh - will give that a shot asap. Having a 124 to 125 short ... likely to damage the chip? Or just stop it working until the short is gone?

(please say it's non fatal)

And I'll have to look closely at my backup machine - it's a mark2 not a 2a, and the last time it had anything done was a long time ago - maybe fun to listen to some stuff that's on it...I went through a phase of deleting things, before realising large disks were a better solution.

Gotta be optimistic. At the low voltages and currents involved in logic and CPU circuitry it's quite hard to destroy something. Not impossible though, so it's always a risk.

Have you tried continuity testing to find the short? Probe the edge of the pads, not the CPU. I suppose the other thing to check is that you could have wicked all the solder out of the connection, such that the pin is not electrically connected to the pad. Unlikely, but possible. To correct this if it is a problem, apply a tiny amount of solder to the fluxed pad and it will wick under the pin. BTW, you really need to use a 0.4mm tip for the CPU connection. Anything larger is a pain to work with.

Thanks Genixia,

Will try to get a chance to check that too - think I should have got a smaller bit - my smallest is a 0.6mm. Still - I'll be optimistic, and learn from my mistakes (next time I'll probably pay someone with better tools to have a shot:-)

Well - just saved the day before heading off for long weekend in the Highlands. I had thought the spare would get some use, but I managed to sort the short (with lots of flux, and the smallest solder wick I have ever seen)

The RAM chips are still there, and all solder joints appear good - I just removed the connection to the ARM (and the solder mess I made around pin 123 etc) so at some point I need to redo that link. Pins 14 on the RAM still look strong so hopefully I can successfully do it next time.

Thanks for the advice Genixia.

Quote:
Thanks for the advice Genixia.

No problem. Glad to hear to found the short.